Published international patent application WO 00/39506 provides a general disclosure of a computer controlled method and system for controlled natural ventilation of ventilation zones in a building by adjustment of passive ventilation devices, typically in the form of openable window sections in building facades or other forms of openable facade sections such as adjustable ventilation dampers, grids and similar devices. The control strategy followed in this prior art method involves periodically repeated estimation of the ventilation demand of a zone from a physical parameter such as the volume of the zone, a target value for the indoor temperature of the zone and measurement of actual indoor and out door temperatures, correction of the estimated demand in dependence of additional indoor climatic variables such as CO2 content to determine an adjustment factor for each ventilation device belonging to the zone and individual correction of adjustments factors thus determined in dependence of additional outdoor climatic variable such as wind load and direction and/or a user actuated adjustment of a ventilation device.
In published international patent application WO 02/01116 a further development of this method to provide comfort optimization for human occupants in the ventilation zone is disclosed.
The ventilation devices employed in such a method or system will as mentioned typically comprise openable windows or other openable facade sections comprising a wing or sash part arranged in a stationary main frame structure to be movable between a closed position and a ventilation position, whereby movement of the wing or sash part is performed by means of at least one electrical operator unit such as a conventional chain operator.
For a relatively simple and small ventilation device a single operator unit may be sufficient for the controlled operation of such a wing or sash part, but frequently a number of operator units will be required for a single ventilation device, e.g. for the movement of a rather heavy wing or sash part and/or for locking and unlocking the wing or sash part in its closed position with respect to the main frame structure in addition to movement of the wing or sash part between its closed position and the ventilation position.
In automatic control systems for natural ventilation of large building comprising a plurality of ventilation zones, a large number of windows placed all over the building may be operated in this way by electrical operator units receiving operating commands from centralized control means incorporating computer means for the determination of control parameters such as a target ventilation position for individual operators in dependence of various climatic parameters, such as air temperature and humidity, CO2 content and wind load as well as external noise from traffic or the like and communication of corresponding control commands to the operator units associated with ventilation devices by remote control. Thereby, a ventilation device such as a window may be moved several times between different positions, which may not always correspond to the closed position or a maximum ventilation position.
For proper exercise of building climate control it is important therefore that exact information of the actual or current positions of all ventilation devices such as windows is made continuously available to the centralized control means.
In prior art electrical window control systems provision of such position information has traditionally been based, however, on relatively simple estimation of the wing or sash position from operation parameters such as the duration and magnitude of the current to a drive motor in an operator unit, using the closed position of the wing or sash part as zero reference. Evidently, use of such an estimation strategy in automatic window control systems would require closing of windows every once in a while in order not to loose track of their position. Otherwise errors in the estimates from the repeated opening and closing movements might accumulate leading to incorrect estimates of the window position.
In a computer-controlled window system for a building disclosed in EP-A2-0 397 179 electrical operation of the locking/unlocking and opening/closing functions of a plurality of windows is accomplished by microprocessors assigned to individual windows or groups of windows. For each window the actual condition of its locking means as well as the actual position of the sash member are communicated to the microprocessor associated with the window from sensor devices arranged at the window and for the overall system these sensor signals are communicated for all windows from the microprocessors to a common central monitoring unit for optical indication of the current condition of each window. Command signals for operation of individual windows or joint operation of a group of windows served by the same microprocessor are communicated to the respective microprocessors either from portable or stationary local remote control units or, via a data bus, from the common central unit. In response to such command signals the function of the microprocessor vis-à-vis a single window is limited to sequential operation of separate motors for the locking/unlocking and the opening/closing functions of the window.
In addition to this relatively limited use of the sensor signals communicated from the individual windows for control purposes the use of several separate sensor devices at each window to provide sensor inputs to the microprocessors requires a corresponding amount of physical wiring between a microprocessor and each window served thereby with resulting complications and costs of installation.